Battery Charging Techniques and Safety

Stereo

Adventurer
I've just been educated on battery care by an excellent, easy-to-understand instructional (http://www.marxrv.com/12volt/12volt.htm) referred to on the extensive thread about a dual battery setup. It led me to some additional questions.

We do dispersed camping and usually get about three or four days off the battery before it drops to about 60%. We have a couple of lights, a 12v faucet pump, and we run the heater for 5 minutes in the morning when it's really cold. To get the battery back up to full charge, we stop at shops/gas stations/tourist information centers and ask if we can plug our Schumacher 15A battery charger (microprocessor controlled; multi-stage charging; float mode monitoring; auto voltage detection) in one of their outdoor outlets to top off our battery. Some let us do it for free, some charge a nominal fee. On fast charge, it takes about 30-60 minutes.

Question: Is it really bad for the battery be charged up on fast charge?

While in Yellowstone National Park, a kindly ranger pointed us to an outdoor outlet even though she wasn't supposed to. I first topped off the cells with tap water - which I now know to be a mistake; I should have used distilled water. Then, in order to avoid detection, I put the battery in a cloth grocery bag and the charger in my backpack, plugged in, and proceeded to read a book to pass the time. When my partner got back from the showers, she noticed there was "water" dripping pretty badly from the bag. I had gotten distracted and the battery was boiling over and spilling acid. We doused everything with gallons of water, enough so that even the bag never burned through.

Question: Why did it boil over? The Schumacher is supposed to have auto shutoff; did it fail? After reading the above instructional, could the problem have had something to do with the battery being in the bag even though it wasn't closed up completely? Was it because I used tap water? I filled the cells to the top; did I overfill them? Should they be filled only to the top of the case, not the top of the fill tubes? I need to know how to prevent it in the future.

Question of safety: We currently keep our battery in our camper under the sink. I have a 4" open vent to the outside, but I don't have the battery in it's own box with a vent hose. It seems there's wide disparity of opinion on whether this is safe or not so I don't think I'll get a definitive answer but I'm curious to hear your opinions. Since we pull the battery out during our trips for charging, we can't lock it in front of the wheel wells when we install our camper and we don't want it in the back of the bed where it could be stolen.

I'm researching how to install a dual battery setup to charge the battery when we're driving from place to place. Question: For those of you who have this setup, do you tend to put your second battery in your engine compartment or in your truck bed or camper and what are the pluses and minuses of one over the other? Can I use a lower gauge wire to the rear if the house battery is close to the starter battery in the engine compartment? (The dual battery thread is recommending 4 ga or even 2 ga between the batteries.) We don't need the setup to provide added power or capacity (no winch, no frig). It would strictly be for charging.

Thanks for your advice!
 

JHa6av8r

Adventurer
I'm curious as to why your using wet cell and not deep-cycle AGM batteries? The AGM will eliminate the venting need. Why not add a portable generator to your set-up for charging as much as I'm against them?
 

DiploStrat

Expedition Leader
I've just been educated on battery care by an excellent, easy-to-understand instructional (http://www.marxrv.com/12volt/12volt.htm) referred to on the extensive thread about a dual battery setup. It led me to some additional questions.

Good link. Here is another: http://handybobsolar.wordpress.com


Question: Is it really bad for the battery be charged up on fast charge?

No, in fact, for AGM batteries, it is almost essential. BUT: All batteries are going to gas to a certain point. AGM batteries need a slightly lower charge voltage (about 14.4v) than open cell (14.8v) but the open cell will need to be topped up periodically. Consider these two articles:

http://www.sterling-power.com/support-faq-2.htm

and:

http://www.sterling-power.com/support-faq-1.htm



Question: Why did it boil over? The Schumacher is supposed to have auto shutoff; did it fail? After reading the above instructional, could the problem have had something to do with the battery being in the bag even though it wasn't closed up completely? Was it because I used tap water? I filled the cells to the top; did I overfill them? Should they be filled only to the top of the case, not the top of the fill tubes? I need to know how to prevent it in the future.

Filled just enough to cover the plates, never to the top of the fill tubes.


I'm researching how to install a dual battery setup to charge the battery when we're driving from place to place. Question: For those of you who have this setup, do you tend to put your second battery in your engine compartment or in your truck bed or camper and what are the pluses and minuses of one over the other? Can I use a lower gauge wire to the rear if the house battery is close to the starter battery in the engine compartment? (The dual battery thread is recommending 4 ga or even 2 ga between the batteries.) We don't need the setup to provide added power or capacity (no winch, no frig). It would strictly be for charging.

Thanks for your advice!

I have done a lot of research on this subject for my new Malayan Tiger and would be happy to share a paper that I have put together on the subject; shoot me an e-mail. It has been reviewed by some reputable experts in the field as well as a battery manufacturer and an inverter/charger manufacturer and found to be correct. (Or at least not seriously incorrect.)

The further apart your batteries, the greater the difference in their construction (starter vs. deep cycle), and the greater the difference in their sizes, the less satisfactory you will find either a diode or a solenoid system.

In my opinion, the best solution is dual alternators with separate regulators, each dedicated to a bank of batteries. Failing that consider:

-- A Battery to Battery Charger. (Companies include Redarc http://www.redarc.com.au, CTEK: http://smartercharger.com, and Sterling Power: http://sterling-power-usa.com/index.aspx

-- An Alternator to Battery Charger. The only source that I know is Sterling Power.

I chose the second option for my Tiger: http://www.pbase.com/diplostrat/ndeke_luka. The first tests indicate that it performs as advertised:

152599134.jpg
152599163.jpg


That is a charge rate of over 170Ah at idle.

Hope this information is helpful.

Edited to add: All information correct to the best of my knowledge and belief. All sources identified so you may asses their possible motives and accuracy. This is what I am doing on my truck, I may be making an expensive mistake, YMMV, etc. Oklahoma 50/50 guarantee: If it breaks in half, you own both pieces. :)
 
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Stereo

Adventurer
I'm curious as to why your using wet cell and not deep-cycle AGM batteries? The AGM will eliminate the venting need.

We didn't want to make a huge investment as we started to explore the truck camping life. When our wet cell dies, we'll explore the AGMs.

[/QUOTE] Why not add a portable generator to your set-up for charging as much as I'm against them?[/QUOTE]

We're adamantly against them too. Silence is golden.
 

DiploStrat

Expedition Leader
My pleasure. N.B. one of our design goals was to avoid having a genset. If the batteries are low, we can simply start the truck engine. Because of the lower pitch, etc., it is much less annoying and less likely to attract the attention of the generator police.
 

DiploStrat

Expedition Leader
FWIW, Charles Sterling, Jr. and the famous Handy Bob are great fans of open cell batteries. They are much cheaper and can be charged harder, as long as you replace evaporation. They excel in stationary instals (e.g., Fifth wheel, narrow boat, etc.) but do less well in high vibration environments like a truck.
 

tanglefoot

ExPoseur
Hi Stereo,

I wanted to put in a plug for solar-charging. It's such as easy way to keep the battery charged and maintained. I would go this route before adding a second battery, myself.

My camper has very low draw (no heater, no fridge), so a single 10-watt panel on the roof is enough to charge and maintain the battery in mine. It's always at full charge in between trips, it maintains the battery nicely while parked over the winter, and it even keeps up pretty well while out camping. I don't have the camper battery connected to the truck at all, and don't need to do any external charging.

Do use a charge controller with panels of 10 watts or more to keep from over-charging the battery. Solar panels operate at about 20V so leaving them connected without a charge controller for long periods can damage the battery. The controller does a great job of automatically maintaining the battery level. Batteries tend to have a longer service life when on a solar charger--they don't get a chance to stay discharged and start sulfating.

Solar systems don't have to be expensive at all. Mine totaled about $50 for the 10W panel and 7-amp (overkill) charge controller. Installation is simple to DIY.

Ebay is a good source for inexpensive solar panels direct from China. This place also has good prices:
http://www.solarblvd.com/Solar-Panels-&-Systems-12-Volt-Solar-Panels/c1_269/index.html

Charge controllers can be found on Ebay/Amazon/other for around $30.

On the battery venting, I have a similar setup--a flooded deep cycle sitting uncovered inside the cabinet, with about a 3" round vent between the cabinet area and the outside wall. I don't have any concerns about it.

Eric
 
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brboyer

New member
Hi Stereo,

I wanted to put in a plug for solar-charging. It's such as easy way to keep the battery charged and maintained. I would go this route before adding a second battery, myself.

My camper has very low draw (no heater, no fridge), so a single 10-watt panel on the roof is enough to charge and maintain the battery in mine. It's always at full charge in between trips, it maintains the battery nicely while parked over the winter, and it even keeps up pretty well while out camping. I don't have the camper battery connected to the truck at all, and don't need to do any external charging.

Do use a charge controller with panels of 10 watts or more to keep from over-charging the battery. Solar panels operate at about 20V so leaving them connected without a charge controller for long periods can damage the battery. The controller does a great job of automatically maintaining the battery level. Batteries tend to have a longer service life when on a solar charger--they don't get a chance to stay discharged and start sulfating.

Solar systems don't have to be expensive at all. Mine totaled about $50 for the 10W panel and 7-amp (overkill) charge controller. Installation is simple to DIY.

Ebay is a good source for inexpensive solar panels direct from China. This place also has good prices:
http://www.solarblvd.com/Solar-Panels-&-Systems-12-Volt-Solar-Panels/c1_269/index.html

Charge controllers can be found on Ebay/Amazon/other for around $30.

On the battery venting, I have a similar setup--a flooded deep cycle sitting uncovered inside the cabinet, with about a 3" round vent between the cabinet area and the outside wall. I don't have any concerns about it.

Eric

A 10 watt panel is almost worse than useless. Solar panels need to be de-rated about 45% to cover for loss inherent in wiring and connections. It might, might, give you enough to cover a battery's self discharge rae and maybe if left alone for a couple months might put a little charge back in the battery.
 

Stereo

Adventurer
Roof mount

Solar systems don't have to be expensive at all. Mine totaled about $50 for the 10W panel and 7-amp (overkill) charge controller. Installation is simple to DIY.

Always good to hear from you, Eric. Thanks for the pricing. I had thought I'd have to spend a couple of hundred to go solar. What you describe is totally doable.

Given concerns about the potential for future leaks with any roof intervention, how did you mount your panel and how did you route your wires into your camper?

For clarification, I wasn't looking to add a another "house" battery. Rather, I was looking to charge it while driving using the straight forward wiring system described here: http://www.expeditionportal.com/forum/threads/77503-How-to-make-a-cheap-isolated-dual-battery-setup-for-50?highlight=how+recharge+battery+driving However, solar holds more appeal in case we stay put for longer stretches, although there's the issue of having to park in the sun. A portable setup seems more appealing to me. A 10w system doesn't look to be too big or heavy to take in and out of the camper, but then there's the concern about wiring distance.
 

DiploStrat

Expedition Leader
… Rather, I was looking to charge it while driving using the straight forward wiring system described here: http://www.expeditionportal.com/for...for-50?highlight=how+recharge+battery+driving However, solar holds more appeal in case we stay put for longer stretches, although there's the issue of having to park in the sun. A portable setup seems more appealing to me. A 10w system doesn't look to be too big or heavy to take in and out of the camper, but then there's the concern about wiring distance.

Remember, the greater the distance between the two batteries and the greater the difference in their construction, the less success you will have with a solenoid system due to voltage drop and differing charge profiles. That said, if you can keep the charging voltage above 14v, at the second battery, not the solenoid, you should be able to get a decent bulk charge. Then, assuming a good charger on your solar rig, you could use that to finish the charge.

This will help you calculate wire sizes: http://www.redarc.com.au/handy-hints/calculator/cable_size_calculator/
 

Stereo

Adventurer
Thanks for the reference. To use the formula, what do I enter for maximum amps? Is it the load I put on the battery with my lights, etc. or something else? I have not yet grasped when volts, amps, and watts come into play.

I'm curious, because when I was on the verge of purchasing a FWC Eagle, the FWC distributor gave me only 14ga wire to connect my starter battery to the camper battery through the camper's existing hookup. Seems like that would have been inadequate.
 

DiploStrat

Expedition Leader
A quick web search will turn up any number of load calculators and the formulae for converting. Grossly, for a 110v appliance, take the amp rating and multiply by 10. So an item that draws, say 1500w at 110v would be 1.5A x 10 = 15A at 12v x the number of hours a day that it is on. So if your microwave draws 1500w @ 110v and you use it twice a day for 15 minutes each time, then you between 7 and 8 AH @ 12v per day. (Hope I got that right!)

So total up your load, both AC and DC, get a guesstimate of your inverter efficiency (start with 90%) and plug the numbers in here: http://www.lifelinebatteries.com/rvsizingac.php

Tons of other calculators here: http://www.rapidtables.com/calc/electric/index.htm

While this table is designed for sizing gensets, the concepts are the same, and it gives some examples of loads you might have: http://www.funroads.com/rv-repair/generators/loadmanagement/

I will bet you a warm beer, or since I will win, a nice Merlot, that the 14g a wire will be next to useless. Review this article: http://www.sterling-power.com/support-faq-1.htm and note why he uses 13v as a starting point.

Hope this helps.
 

tanglefoot

ExPoseur
On solar installation...

My camper already has a section of wiring conduit that goes from the counter top to the ceiling to contain the wires for the interior lights. I simply drilled a hole in the exterior skin of the roof near where the lighting conduit runs, fished the wire to the panel through it (it has some nice, heavy insulation on the wire so I'm not too concerned about chaffing), and ran it through the conduit and into the cabinet area. For sealing, I used a little bit of RV putty (it's also used around exterior seams and lights from the factory) and mashed it around where the panel cable goes through the upper roof aluminum. I mounted the panel to the roof using some brackets from a swing set that Dad had in the junk box.

Although I usually camp in the sun to warm things up in the morning, parking in the shade isn't much of a problem for the electrical system. With the battery being solar-maintained while parked at home, the camper battery is usually over 13v (charging from the engine usually won't fill the camper battery up this much) before I pack up to go camping. Solar panels do produce power in the shade (just not as much), and even most shady spots have sun for some portion of the day.

Winterizing is another advantage of a solar-charger. My parents' camper uses the traditional engine charging to charge the house battery while driving. Not only does it never really seem to put a good charge on the house battery, but while parked for long periods, the house battery charge level can gradually drain until it's under-voltage and the plates start to sulfate (this is the primary reason batteries need to be replaced). My parents usually remove the battery from the camper, lug it into the garage and plug it into a float charger to keep this from happening. When a solar-charged camper is parked outside while not in use, the panel and charge controller keep the camper battery between 13 and 14v all winter. Not only is this great for battery health, but then when you're ready to use the camper again, the house battery is already topped off.

With the use of an RV furnace, you'd probably want a panel larger than 10W. You could probably get by with about a 30W panel, depending on how much the heater is used and what the other loads are.

I remember you mentioning that fuel economy is a concern of yours. Another reason I went the solar route is to reduce electrical load on the engine charging system. Drawing a battery charging load from the engine does make the alternator harder to rotate and increases fuel consumption a slight amount.

On the electrical units, when teaching ham radio theory, we usually use water as an analogy. If you imagine a canal of water, the depth of the water is the voltage measurement--how much energy potential the water has when it is allowed to flow. Current (Amps) is...the current of the water---how much volume passes over a certain point over a unit of time. Power (Watts), the amount of work the energy is doing, is a combination of the current (Amps) and the potential (Volts). It's calculated by multiplying the current (Amps) and the voltage. The total amount of energy, measured in gallons or similar for the water analogy, is expressed as a combination of current (or power) and time--usually Amp-hours for batteries and Watt-hours for electrical service to a home or business. E.g., an 800 Amp-hour (AH) battery has the ability to provide about 1 Amp of current for 800 hours (or 2 Amps for 400 hours, etc.) A 60-watt light bulb operated for 1 hour uses 60 Watt-hours of energy.

Just a note that on the microwave oven example, the power measurement (1500W) is conserved between the different voltages. 1500W at 120V is 12.5A but 1500W at 12V is 125A. Using that a half-hour per day requires 62.5 AH, not taking inverter losses and other losses into account (one reason I don't like microwave ovens).
 
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