Questions about charging 6 volt batteries with Atlen or Harbor Freight generators?

magentawave

Adventurer
I was thinking of buying (or possibly building) a gas powered 12 volt DC battery charger to charge two to four 6 volt batteries (Trojan T105's or similar) for cloudy days when solar can't keep up.

The Alten 12 volt Honda powered charger at $1300 (aaargh!) puts out 27 amps at 3500 RPM's (half throttle).

Harbor Freight has two cheap generators that claim to generate "2200 running watts" ($500) and the other does "700 running watts" ($130). I don't see anything on the HF site that tells me how many RPM's they are doing during that "running time."

Here are my questions please...

1) Since the Atlen puts out 27 amps at half throttle (3500 RPM's), does that mean it would take about two hours to charge two 50% discharged Trojan T105's to 100%?

2) Does HF's $500 "2200 running watts" generator mean that it will produce 183 amps? If so, can you please tell me how many amps would be used to charge my 6 volt batteries? And same question for HF's $130 "700 running watts" generator that is supposed to put out 58 amps?

3) The reviews are pretty good at the HF site, but have you used one of those HF generators for a long enough period of time to be able to judge its reliability and longevity?

Thanks! :)
 

Curmudgeon

Adventurer
2) Does HF's $500 "2200 running watts" generator mean that it will produce 183 amps? If so, can you please tell me how many amps would be used to charge my 6 volt batteries? And same question for HF's $130 "700 running watts" generator that is supposed to put out 58 amps?
You're comparing machines that are not comparable. The Alten is strictly 12 volt output. The two HF generators are primarily 120 volt output, although the 2200 has a 12 volt receptacle that outpts 8.3 amps. The 700 will produce about 6 amps continuous. If the output was 2200 watts at 12 volts, that would be 183 amps. But 2200 watts at 120 volts is one tenth that much, 18 amps.

Did you notice the noise level on the 700? It's a two cycle and emits 91db. That's very loud. A typical lawn mower is 90db.
 

Haf-E

Expedition Leader
If the two series connected Trojan T105 batteries were at a 50% state of charge level - then you would need to put back in 110 amp-hours + a bit more to make up for losses. So that would require about 4 hours if the generator was producing 27 amps DC when at half throttle.

The Alten looks pretty good - the harbor freight gens tend to die if used for extended periods of operation - poor quality from my limited experience with them.
 

magentawave

Adventurer
I was just looking at the cheap prices to see if I could make an HF generator work so thanks for clearing that up. And yes, they are loud.

You're comparing machines that are not comparable. The Alten is strictly 12 volt output. The two HF generators are primarily 120 volt output, although the 2200 has a 12 volt receptacle that outpts 8.3 amps. The 700 will produce about 6 amps continuous. If the output was 2200 watts at 12 volts, that would be 183 amps. But 2200 watts at 120 volts is one tenth that much, 18 amps.

Did you notice the noise level on the 700? It's a two cycle and emits 91db. That's very loud. A typical lawn mower is 90db.
 

magentawave

Adventurer
Thank you.

Do you guys know about anything about building your own DC charger? This guy built one that was inspired from this page.

If the two series connected Trojan T105 batteries were at a 50% state of charge level - then you would need to put back in 110 amp-hours + a bit more to make up for losses. So that would require about 4 hours if the generator was producing 27 amps DC when at half throttle.

The Alten looks pretty good - the harbor freight gens tend to die if used for extended periods of operation - poor quality from my limited experience with them.
 
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Haf-E

Expedition Leader
I was going to mention that - it is pretty simple - and a DC output generator is actually a better solution as long as you have a decent quality DC to AC inverter to run the loads. Its better in that you can operate a DC output generator at different RPMs - so it can be quieter when you want or can be "tapered" to allow finishing charging or equalize charging at lower current levels.

The site "epicenter" seems to have good information and some nice parts - I would check them out more. You also might check out back issues of the magazine "Home Power" which has done a number of articles in the past on making and using DC output generators.
 

Haf-E

Expedition Leader
There are others - but they tend to be even more expensive or made for 24vdc systems used on boats etc. Also, since they are fairly easy to make (as shown on the EpiCenter site) the market tends to be small. There are a number of Youtube videos as well.
 

dwh

Tail-End Charlie
I bought one of the HF 2-stroke generators this year after my last one (Champion 42431) finally developed a crack in a valve at around 1200 hours (and was WAY out of warranty). I would have gladly bought another little Champ - great generator - but even at 1200w continuous it was still bigger than I needed for camper battery charging, and I wanted to try something smaller. HF puts out email coupons and the 2-stroker goes on sale for a few days every month for 99 bucks if you have the coupon it for that month.

Eventually when the 2-stoke dies, I'll buy another little Champ. It's just a lot better (and quieter), even though it's bigger than what I need. With an 80cc engine compared to the 63cc in the 2-stroke, gas consumption is comparable. Plus the warranty on the Champ is 2 years and the 2-stoke 90 days - and Champion is in SoCal and is crazy about taking care of customers. EXCELLENT customer service.


I just bought a couple weeks ago a Stanley BC1509 15a battery charger that I spotted at Lowe's for 50 bucks. I bought the charger just to play with the desulfation mode, but it actually does a damned good job of battery charging.

The 2-stroke gen I got says on the box 800w continuous, 900w surge. It also says on the box in the list of crap it will run, "15a battery charger". It has a decal on the unit that says 6.5a max. The Stanley specs say it draws 4a max.

The generator will run the charger when the charger is putting out the full 15a. You can certainly hear that the gen is loaded, but it handles it just fine. However, voltage drops to around 100v. This is not a problem, and as it turns out, the Stanley charger manual says it compensates for low voltage on the input side (I'm assuming for when people run it from a long extension cord).


The charger does not have an on/off switch. Instructions say to connect it first to the battery, then to AC power. Opposite to disconnect. Fine - it doesn't have a problem being plugged in when the generator runs out of fuel. I've done it, and it behaves exactly the same as unplugging it from shore power.


The 2-stroke is loud, but not as loud as I expected. I have a generator box I built on the back of my camper, and when the gen is in there, it's not irritating unless you are standing fairly close (10' or less) and directly in the path of the exhaust. Of course, a campsite generator Nazi would crap their pants over it, but I generally avoid campsites and people whenever possible (I have friends with property both in the desert and in the mountains and usually have the whole place to myself), so I haven't have any problem with it. If you were running it in the driveway in the suburbs, I would expect some neighbor to get sick of it after a few hours. I don't have any neighbors - I already killed them all. :D

Specs say it holds 1g of gas. Mine doesn't. 1g will overflow the tank (don't ask how I know this). Mine holds .9g. Takes 2.5 oz. of 2-stroke oil per gallon. If you buy it, don't buy the 8 oz. bottle from HF for 5 bucks. Buy a 32 oz. quart from an auto parts store for the same price.

All the net reviews say to replace the spark plug with a quality plug. I bought a Champion plug for it, but still haven't installed it because the gen works just fine. Eventually I'll get around to changing it and see if the better plug really makes any difference.

When new, the gen ran 8 hours on .9g. After break-in...maybe 5 tankfuls of gas...its now getting around 10-12 hours on a tank, running only the battery charger. That's a little deceptive, since with my single 12v house battery, the charger will get into float mode long before that, so the last few hours there is really basically no load on the gen.



For a cheap setup for a bigger bank, I would probably go with the little Champ, which I got for 200 bucks, and free shipping from a Champion fulfillment web site that appears to be gone now. That one held 1.2g of gas and ran 14 hours after break-in on a full tank doing only battery charging. The Stanley charger works well - and except for the 6a unit, comes with a desulfation mode which I have tried and it does work. They have a 6a unit for 30 bucks, the 15a for 50 and they also make a 25a and a 40a. Lowe's didn't have the 25a, but the 40 was, IIRC, 80 bucks.

For a proper setup for a bigger bank, I'd go with a Honda or Yamaha 2000w inveter gen and a 55a Iota battery charger. But that'd run up around 1500 bucks for the whole setup.
 

dwh

Tail-End Charlie
Trojan 6v T-105s are 225ah @ 20hr rate. Two 6v rigged in a series string to get 12v will be 225ah. Two strings rigged in parallel to get 12v will be 450ah. At 50% Depth of Discharge, you'll need 225ah+ (generally around 20% extra) to get them fully charged. So figure 275ah for a full recharge from 50% DoD.

The Alten in the OP's link puts out 55a max and appears from the brochure to operate as a constant voltage power supply. Brochure says it puts out a regulated voltage of either 14.0v or 14.8v. The T-105s would love the 14.8v, but use a bit of extra water.


I would GUESS (yes, just a guess, but I'm a pretty good guesser) based on what I see in the Alten docs, that the Alten would get the 4 T-105 12v 50% DoD bank up to around 80% in maybe 5 or 6 hours, and then take perhaps another 6-8 hours to fully finish the charge.

Could be a LOT longer though. If the bank reaches a surface charge of 14.8 fairly quickly then it'll be hours and hours of steadily decreasing amp flow since the battery is being charged in constant voltage mode rather than constant current mode.
 

magentawave

Adventurer
Thanks for all of the information everybody. This has been very useful in helping me to make a decision. So with charging times that long, I don't think I'll get a charger. If I hit consecutive cloudy days then I'll just have to conserve my energy usage more than usual.


Trojan 6v T-105s are 225ah @ 20hr rate. Two 6v rigged in a series string to get 12v will be 225ah. Two strings rigged in parallel to get 12v will be 450ah. At 50% Depth of Discharge, you'll need 225ah+ (generally around 20% extra) to get them fully charged. So figure 275ah for a full recharge from 50% DoD.

The Alten in the OP's link puts out 55a max and appears from the brochure to operate as a constant voltage power supply. Brochure says it puts out a regulated voltage of either 14.0v or 14.8v. The T-105s would love the 14.8v, but use a bit of extra water.


I would GUESS (yes, just a guess, but I'm a pretty good guesser) based on what I see in the Alten docs, that the Alten would get the 4 T-105 12v 50% DoD bank up to around 80% in maybe 5 or 6 hours, and then take perhaps another 6-8 hours to fully finish the charge.

Could be a LOT longer though. If the bank reaches a surface charge of 14.8 fairly quickly then it'll be hours and hours of steadily decreasing amp flow since the battery is being charged in constant voltage mode rather than constant current mode.
 

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