Charging batteries with generator?

Submitted: Saturday, May 03, 2003 at 01:27
ThreadID: 4705 Views:18350 Replies:7 FollowUps:4
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Advice Needed!

I currently have 2 x 90 amp hour deep cycle batteries in my campervan which are charged via an Anderson plug when travelling.

When I am camped for an extended period of time I have a generator to assist in maintaining the charge.
The generator has both AC and DC output however the DC output of 10 amps is not regulated and I am concerned of frying my batteries.

My question is should i buy a regulator for the DC output or would it be better to buy a smart charger to run off the AC output? If I buy a smart charger I would want one that would have an output of at least 10 amps. (any recomendations on the product name and or suppliers would be great)

What would be the maximum amperage that I could use to recharge the deep cycle batteries without damaging them?

Any advice would be greatly appreciated.

Thanks in advance

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Reply By: Solar King - Saturday, May 03, 2003 at 09:56

Saturday, May 03, 2003 at 09:56
10 amps in is not a lot at all for 180 amp hr total battery size. With 10 amps it would be difficult to 'fry' your batteries. It will take all day to charge them back up if you let them get down to 50% capacity. You could charge your combined battery bank at 20 amps max without being a problem. Use a volt meter to see when your batteries come up to full voltage. You should know roughly how much power you are using a day and if you have a decent digital voltmeter permenantly connected you can see the battery voltage before you start charging so this would give you a good idea at what state of charge the batteries are and how much they need. You are going to run that generator for a large part of the day if you are using a 12v fridge and other gear.
Running a generator and then a 240v battery charger just makes it more inefficient than ever.
AnswerID: 19045

Reply By: David N. - Saturday, May 03, 2003 at 10:28

Saturday, May 03, 2003 at 10:28
I assume your batteries are wet cell?
With 10 Amps into that capacity it's near IMPOSSIBLE to "fry" your wet cell batteries.
A bit of overcharge occasionally will not hurt your batteries at all, provided you watch electrolyte levels.
You'll do far more harm by flattening them too much (say beyond 70% discharge) and by not charging them ASAP after discharge.
Just remember, Lead Acid batteries like being fully charged, and hate being flat.
If you want to go into smart chargers the sky is the limit- talk to a specialist, but be prepared for some serious dollars.
AnswerID: 19048

Follow Up By: David N. - Saturday, May 03, 2003 at 10:41

Saturday, May 03, 2003 at 10:41
Also if you were still concerned- a good compromise would be an automatic 240 v charger- eg: Supercheap sell one for about $150 which puts out about 12? Amps if my memory serves me correctly, then cuts off when battery is fairly full. If the batteries were well down you could easily use both to put in over 20 amps into your batteries.
But do buy yourself a good digital multimeter and never flatten the Bat beyond 11.5v under load and dont charge much over 15 v normally.
Depending on temperature, a fully charged battery which has been sitting for quite some time (many hours) since charge or discharge is about 12.75 volts. An EMPTY battery (after the same time sitting) would be 11.7 -11.8volts approx. Remember both these figures do NOT apply on charge or under discharge.
I try never to discharge a battery beyond 70% flat and get good life from the battery.
FollowupID: 11956

Reply By: Member- Rox - Sunday, May 04, 2003 at 12:50

Sunday, May 04, 2003 at 12:50

I have been looking into this as well and have decided to buy a battery charger from 12 volt shop
10amp = $299
20 amp = $399
I am going for the larger one. They are both 3 stage charges and can be left permatly on charge e.g., home, c/van park.

I have a honda eu1 with a dc out put but was told that this doesn't stop when full and will damage batteries ( use only in an emergancy)

ATB, RoxEaster at Yardie creek
AnswerID: 19086

Follow Up By: William - Sunday, May 04, 2003 at 19:08

Sunday, May 04, 2003 at 19:08
Have you not researched all the feed back from the 12Volt Shop. Perhaps you need to look at some other websites about them.

Do you realise that the 20 amp charger will probably put out 12 amps at best and probably 10 amps.

FollowupID: 12002

Follow Up By: Cobes - Sunday, May 04, 2003 at 20:46

Sunday, May 04, 2003 at 20:46
Hi Rox,
I was at the Sydney show last week and saw a Hawkins 15 amp smart charger for $249. (I think same as 3 stage charger)
The constant output was 12.5 amps.
I wish now that I had of bought it as at the time I didn't really know what they were valued at.

If for example you purchased your 20 amp charger which had a continuous amperage of say 12-15 amps would you consider also charging from you DC output at the same time?

Would you just simply connect the two to the battery?
As you were nearing full charge you could remove the DC lead and let the 3 stage charger complete the final amount to fully charge the battery?
I guess this would be more economical if charging from a gene.
What are your thoughts?

FollowupID: 12013

Reply By: Dozer - Sunday, May 04, 2003 at 13:26

Sunday, May 04, 2003 at 13:26
Hi Cobes
Once the charger(whichever) is put on the batteries, they will quickly become surface charged, and a volt meter wont help determine their charge state.Thats where a hydrometer comes in handy. They will need a long time to recharge, as the design of deep cycle batteries also means deep recharging is necessary. Best way would be to put them on a regulated 240v recharger, but in the sticks, the generator will do to top them up. When you say the dc is unregulated, i disagree. It is regulated to 12 volts, and can put out a charge of 10 amps max if the battery will take it, but remember that the resistance in a battery changes from empty to full, and therefore in laymans turms, the battery will take what it is given but as it fills, the generator will not be able to put the 10 amps in as easily as it did when the battery was empty.
the formular is volts=resistance x amps
v is almost constant (regulated)
r changes with charge state of battery
a therefore must change to balance the equasion
Hope this is right
AnswerID: 19092

Follow Up By: Cobes - Sunday, May 04, 2003 at 20:50

Sunday, May 04, 2003 at 20:50
Hi Dozer,
Thanks for your response.
I will look around for a decent 3 stage charger.

FollowupID: 12015

Reply By: Member- Rox - Sunday, May 04, 2003 at 21:42

Sunday, May 04, 2003 at 21:42
'Have you not researched all the feed back from the 12Volt Shop. Perhaps you need to look at some other websites about them. " Please in form me.Easter at Yardie creek
AnswerID: 19118

Reply By: Member- Rox - Sunday, May 04, 2003 at 21:51

Sunday, May 04, 2003 at 21:51
I saw lots of people at caravan show recharging batteries via EU10 gen sets directly of the dc supply. I latter asked 12 volt shop ant they said its not regulated and for long life use a proper 3 stage charger other wise you may cook your bateries. some said they only tack what they need but 12 volt shop sain diferent.

I'de like to know if thats just a sales pitch!!!?Around Oz 06/2004
AnswerID: 19121

Reply By: -OzyGuy- - Friday, May 09, 2003 at 16:29

Friday, May 09, 2003 at 16:29
I have two Delco, 80 amp/hr deep cycle batteries wired in parallel, (160 amp/hrs, $270, total) managed by a Piranha DBE150S electronic Dual Battery Isolator, charged by the vehicle altinator while driving and also an 80 watt Solarex Solar pannel when stationary in the bush.
I use a 10 amp battery charger, charging through a trickle charge add on module from K-Mart, when in the city, it remains connected at all times. I think both units were only about $70 or $80 each??
The dual battery setup only powers a 50 ltr fridge/freezer, radio and camp lights etc, I don't have battery hassles, as is stated elsewhere they Must be kept fully charged to work at their peak and retain amps.
AnswerID: 19513

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