How many amps can I bang into my leisure batteries without cooking them?

[jongood]

I think you are been a tad hopeful there jon..
Very unlikely to work out quite like that..
Multiple charging sources seldom work that way.. if your batteries are very low you may get an initial high input but ill bet it will tail off very quickly and you will get one source dominant..the others seeing a rising voltage on the battery bank and contributing very little or nothing..
You will only know when you have tried it and monitored it but those would be my thoughts..
Usually my mains charger was the dominant source if on ehu..solar contributes nothing when on mains.. matters not how much you have on the roof..
Battery to battery obviously when on the move..
And solar when there are no other sources in play..
Andy..

Good point Andy

The hook up is not an issue because its not something we often take, in fact the point of this is to enable us to stay off grid for longer ( for ever would be even better) but yes I get the point that if the battery voltage rises too high it could be shutting off

I emailed Votronic and asked them what they think. But have also wondered if I could fit a larger 12 volt alternator?

 

[andy63]

Good point Andy

The hook up is not an issue because its not something we often take, in fact the point of this is to enable us to stay off grid for longer ( for ever would be even better) but yes I get the point that if the battery voltage rises too high it could be shutting off

I emailed Votronic and asked them what they think. But have also wondered if I could fit a larger 12 volt alternator?

But thats the trouble..you are asking a question that is so difficult to answer..your system is unique to you but you will get to know it by watching it..

On the larger alternator front my thoughts would be more inclined towards a bigger capacity battery to battery charger is you really want the best out of charging on the move....
We are nearly back full circle here..if you want rapid energy replacement...you need lithium..

 

[jongood]

But thats the trouble..you are asking a question that is so difficult to answer..your system is unique to you but you will get to know it by watching it..

On the larger alternator front my thoughts would be more inclined towards a bigger capacity battery to battery charger is you really want the best out of charging on the move....
We are nearly back full circle here..if you want rapid energy replacement...you need lithium..

Why wouldnt I have the same problem with Lithium?

 

[andy63]

Why wouldnt I have the same problem with Lithium?

True
you would have the same issue with charging sources..but the lithium would take all a source was designed to give...until full.. and so much faster than charging a large gell bank..
I can see you arnt going to bite the bullet

Have to admit to been impressed with your gel discharge tests
Andy

 

[jongood]

I can see you arnt going to bite the bullet

I'm struggling to justify it Andy

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[jongood]

The other thing I discovered yesterday was that there apparently isnt much going into the batteries from the mains chargers. I have 2 of them both rated at 35amps but charging my thoroughly discharged batteries one was putting 12 amps in and the other 5 amps and turning one or the other off makes no difference. any ideas on that one?

 

[funflair]

The other thing I discovered yesterday was that there apparently isnt much going into the batteries from the mains chargers. I have 2 of them both rated at 35amps but charging my thoroughly discharged batteries one was putting 12 amps in and the other 5 amps and turning one or the other off makes no difference. any ideas on that one?

Morning Jon

That goes back to what Andy was saying earlier about Lithium, they are greedy and will take whatever charge you throw at them, my understanding is it is down to the internal resistance of the battery and this is much higher with Pb than lithium so they can only take so much although you numbers seem really low, I wonder what would happen if you turn off one charger?
.

 

[Lenny HB]

The other thing I discovered yesterday was that there apparently isnt much going into the batteries from the mains chargers. I have 2 of them both rated at 35amps but charging my thoroughly discharged batteries one was putting 12 amps in and the other 5 amps and turning one or the other off makes no difference. any ideas on that one?

Gels have a very low internal resistance when flat wondering it they are overloading the chargers.

 

[JockandRita]

Jon, if I may, I'd like to relay our recent experiences with alternator/split charging.

We overnighted at Canterbury, then Bray Dunes on the way to Germany in September. We used the inverter at both locations for the 900w kettle and toaster. At Bray Dunes we had a full day's glorious sunshine, banging in the amps from the 4 x solar panels. On the morning of leaving Bray Dunes we once again used the inverter for a quick coffee before hitting the road for the long haul.
When I started the engine, immediately a charge of 37A was observed going into the 4 x 80A batteries from the alternator.
6/7 x hours later we arrived at Reil, with only a quick fuel and toilet stop at Luxembourg on the way, and no inverter usage.
When we plugged in to EHU upon arrival at Reil, to my astonishment the batteries were still taking over 16A charge. 24 x hours later, they were still taking a charge, albeit a low conditioning charge of around 3 - 4A.

Prior to this, I had been put off fitting a B2B, on the basis that the cable diameter installed by N&B, to and from the split charge relay, was possibly greater in diameter than what most converters installed, and that the charge from the alternator would be sufficient. As a result of the above findings, I'm not convinced, and have just fitted a 12v 60A B2B, however, I'm not in a position yet to be able to check out the duration of charge, compared to that from the alternator alone. A winter weekend away might be a good experiment, to suss out any improvement on charging times.

Edited............... My previous experience with a 12/50 B2B after a winter weekend away, was a good charge during a 2-3 hour drive, with the final conditioning charge from EHU starting at around 7A, and reducing over a few hours.

HTH,

Jock.

 

[JockandRita]

I have edited my above post, in case you haven't seen that Jon.

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[jongood]

Gels have a very low internal resistance when flat wondering it they are overloading the chargers.

I'm not understanding this Lenny. Wouldnt a low internal resistance mean that they would take more?
The chargers are 2 x 35 amps, second one fitted by Riepperts

 

[Lenny HB]

I'm not understanding this Lenny. Wouldnt a low internal resistance mean that they would take more?
The chargers are 2 x 35 amps, second one fitted by Riepperts

Yes that's my point, overloads the charger and the charger shuts down or reduces its output.

 

[funflair]

Yes that's my point, overloads the charger and the charger shuts down or reduces its output.

That's interesting Lenny but still pretty high compared to LiFePO4 I guess, so you are suggesting that as the batteries become charged the amps that the mains charger delivers should increase.

 

[Lenny HB]

That's interesting Lenny but still pretty high compared to LiFePO4 I guess, so you are suggesting that as the batteries become charged the amps that the mains charger delivers should increase.

Yes, need to wait and see what happens.

 

[68c]

The other thing I discovered yesterday was that there apparently isnt much going into the batteries from the mains chargers. I have 2 of them both rated at 35amps but charging my thoroughly discharged batteries one was putting 12 amps in and the other 5 amps and turning one or the other off makes no difference. any ideas on that one?

How accurate are your chargers? If one outputs higher than the other, even if by a small amount, the higher voltage one would carry most of the load. Even wire lengths could have an effect.

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[jongood]

Ive been having a look at this

<Broken link removed>

This takes the input from solar and then blends in battery to give up to 50 amps. my thinking is that 50 amps not competing could work. The downside are there is no display option and the open circuit voltage of the solar panels has to be below 32v.

 

[jongood]

How accurate are your chargers? If one outputs higher than the other, even if by a small amount, the higher voltage one would carry most of the load. Even wire lengths could have an effect.

The second one was added at a later date and the cable from that goes straight to the battery whereas the original goes through an isolator and a 300 amp fuse.

However turning either one off doesnt make the other give more.

 

[jongood]

I have edited my above post, in case you haven't seen that Jon.

Thanks Jock I'm looking forward to hearing how it works for you. The battery cables on the clou are huge, well over twice the size of regular battery cables.

 

[funflair]

How accurate are your chargers? If one outputs higher than the other, even if by a small amount, the higher voltage one would carry most of the load. Even wire lengths could have an effect.

I am no expert at all but isn't the bulk phase at contact current and then after reaching a given voltage it goes to constant volts absorb and float, yes I agree that one charger will see the trigger voltage first and cut back to absorb voltage leaving the other one to bulk charge a little longer before also seeing the trigger voltage and cutting back to absorb, that seemed to be how our two solar controllers behaved.

 

[funflair]

deleted
.

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[jongood]

I've found the 12volt alternator and this

So having fixed it and tightened the belt up I'm now getting 36 amps but still nothing like the 65 amps that it says on the side of the alternator. Ive had the clamp meter around both ends.

 

[funflair]

The -ve looks a bit minimalist Jon, the connection looks good would you want 65A through that
.

 

[jongood]

The -ve looks a bit minimalist Jon, the connection looks good would you want 65A through that
.

It doesnt look very meaty does it Martin. I temporarily joined it with a terminal block but I've had another look and the vibration from the engine has disturbed that so might get some more out of it with a proper connection. M Son in law ( Sparky) has got a big crimper but I'm wondering if I could extend it and solder it.

 

[Lenny HB]

I've found the 12volt alternator and thisView attachment 439976

So having fixed it and tightened the belt up I'm now getting 36 amps but still nothing like the 65 amps that it says on the side of the alternator. Ive had the clamp meter around both ends.

With those size cables you would be doing well to get 10 amps. I would rewire with at least 50 mm sq cable.

 

[funflair]

With those size cables you would be doing well to get 10 amps. I would rewire with at least 50 mm sq cable.

That might pull the alternator off it's bracket

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[jongood]

With those size cables you would be doing well to get 10 amps. I would rewire with at least 50 mm sq cable.

Ive now got the whole thing off and all the connections are looking very crappy so Ive got a new plug on order. the blurb with the plug says 9.5mm, bearing in mind that it joins within a couple of inches to the much larger cable to go to the back, should this be enough? If I can get 50amps at the battery I reckon I'm happy

 

[Lenny HB]

How long is the short run to the connector?

 

[68c]

I am no expert at all but isn't the bulk phase at contact current and then after reaching a given voltage it goes to constant volts absorb and float, yes I agree that one charger will see the trigger voltage first and cut back to absorb voltage leaving the other one to bulk charge a little longer before also seeing the trigger voltage and cutting back to absorb, that seemed to be how our two solar controllers behaved.

Yes, I agree with you. However as you then rely on the two chargers to decide when to change to absortion and then float, it may be wiser to use both for the bulk then only one for the rest. As to why no noticeable change when switching off one charger, I still feel that is due to the slight variation in output. They are probably close enough that you do not see the charge difference on your meter.

 

[jongood]

How long is the short run to the connector?

about 50mm

 

[jongood]

Yes, I agree with you. However as you then rely on the two chargers to decide when to change to absortion and then float, it may be wiser to use both for the bulk then only one for the rest. As to why no noticeable change when switching off one charger, I still feel that is due to the slight variation in output. They are probably close enough that you do not see the charge difference on your meter.

One is putting in12amps and the other about 5. is that not a big difference?

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