Twin batteries

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Bongolia
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Twin batteries

Post by Bongolia » Sat Jul 27, 2019 3:48 pm

Right so I have fitted an extra leisure battery to the van wired in parallel under the seat.
I have a sergeant ec500 PSU and a px300 battery charger with ec480 control panel.
I thought I had picked an equal battery to the existing one but it is actually a calcium battery.
So the problem I have is that the older one (by a year) reaches it full state of charge but the calcium doesnt seem to ever get there.
If I charge individually then all seems good.
Do I need matching chemistry batteries and is the older lead acid signal the charger to switch down the input?
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Re: Twin batteries

Post by g8dhe » Sat Jul 27, 2019 6:15 pm

Yes ALWAYS without fail match the chemistry!
Having a problem with people recommending using AGM leisure batteries on FB, whilst using standard lead acid starter batteries, of course they work well now and will do so for about a year when the AGM will start complaining because the Alternator keeps charging it at 14.4 volts (or even higher) when its full, this causes gassing and loss of electrolyte which is much reduced to start with in AGM batteries, there meant to be dropped down to float charge after reaching high 90%+ charge states.....
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Re: Twin batteries

Post by Bongolia » Sat Jul 27, 2019 8:13 pm

Thanks Geoff.
To clarify neither battery is used for the starter a standard lead acid is used for that. Clearly I need to match up chemistry, would you go with two calcium or two conventional lead acid?
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Re: Twin batteries

Post by g8dhe » Sat Jul 27, 2019 8:23 pm

Yes appreciate they aren't used for starting but the vehicle alternators only have one setting! In some more modern cars they are pre-configured for the type of battery supplied with the vehicle, but again paralleling additional batteries assumes that there of the same chemical style and also of similar age, mixing new batteries with much older batteries can have similar results.

I've personally come to the conclusion that its more reliable and cost effective to use a cheaper battery and plan to replace it every 2 years and then get the nice feeling when it lasts 3 or more years ;-)
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Re: Twin batteries

Post by Roy748 » Sun Jul 28, 2019 2:04 pm

Can I ask. I have seen a number of bongos with solar panels fitted, now if you can as you mention over charge the battery, will having solar panels on the vehicle do this, if no current is being pulled for a length of time.
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Re: Twin batteries

Post by g8dhe » Sun Jul 28, 2019 3:00 pm

:-) YES and NO!
Lets explain, the controllers for most Solar power systems understand the different battery types and how they should be handled, when you install the system you choose the type of lead acid battery your using, which is fine as far as it goes, the controllers will behave correctly.
However the controllers don't know about your Split Charge Relay system that also charges the battery from the alternator when your driving, or the charger(possibly) built into the EHU setup ..... Neither the alternator or the EHU based charger normally understand the different battery types, nor do they know about the other methods of charging that will be going on in parallel.
So the poor battery gets charged via different sources (not a problem in itself) some of which might understand the different battery types and some that don't! These are all reasons why I choose to use the the most rugged type of Lead Acid battery, which also happens to be the cheapest, the battery will suffer the least and it can be replaced.
This is another reason why when people fit "Intelligent" chargers I have to smile, IF they are the only charging method then not a problem, they will handle the battery correctly, but they don't know about the other charging methods nor are they built to understand that there is also loads on the battery whilst its charging the battery, so half the current (or so) is NOT going to the battery at all but being used to light the LED's, Lights and charge your Phone, hence when the correct amount of current for the right amount of time has passed, they then check the voltage and the "intelligence" gets confused because it doesn't match what is expected .....
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Re: Twin batteries

Post by Roy748 » Sun Jul 28, 2019 5:23 pm

Thank you for the explanation, I always wondered what the effect on a battery permanently fixed solar panels had.
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Re: Twin batteries

Post by Bongolia » Sun Aug 25, 2019 5:20 pm

g8dhe wrote: Sun Jul 28, 2019 3:00 pm :-) YES and NO!
Lets explain, the controllers for most Solar power systems understand the different battery types and how they should be handled, when you install the system you choose the type of lead acid battery your using, which is fine as far as it goes, the controllers will behave correctly.
However the controllers don't know about your Split Charge Relay system that also charges the battery from the alternator when your driving, or the charger(possibly) built into the EHU setup ..... Neither the alternator or the EHU based charger normally understand the different battery types, nor do they know about the other methods of charging that will be going on in parallel.
So the poor battery gets charged via different sources (not a problem in itself) some of which might understand the different battery types and some that don't! These are all reasons why I choose to use the the most rugged type of Lead Acid battery, which also happens to be the cheapest, the battery will suffer the least and it can be replaced.
This is another reason why when people fit "Intelligent" chargers I have to smile, IF they are the only charging method then not a problem, they will handle the battery correctly, but they don't know about the other charging methods nor are they built to understand that there is also loads on the battery whilst its charging the battery, so half the current (or so) is NOT going to the battery at all but being used to light the LED's, Lights and charge your Phone, hence when the correct amount of current for the right amount of time has passed, they then check the voltage and the "intelligence" gets confused because it doesn't match what is expected .....
So would it make sense to isolate/switch off the solar panel when on hook up?
P.S. I am currently fitting out the Waspy with electrics. I have a twin 13amp outlet mounted in a trim panel that I may need to remove from time to time. I obviously want to avoid disconnecting the 13 socket each time so what cable connector would you suggest?
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Re: Twin batteries

Post by g8dhe » Sun Aug 25, 2019 5:37 pm

Not really, if you mix battery types then you can never satisfy both batteries - calcium however is less involved with actual battery chemistry, its more to protect against sulfation problems and added to give the lead plates more structural strength also helps reduce self discharge.

As to mains connectors probably something from the IEC standards would be best https://en.wikipedia.org/wiki/IEC_60320
https://uk.rs-online.com/web/c/connecto ... onnectors/
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Re: Twin batteries

Post by Roy748 » Mon Aug 26, 2019 2:52 pm

Hello Geoff
This topic has my interest as when my van is parked up I have the leisure battery hooked up to a 40watt solar panel. When driving its charged via a split charger. When camping for 3 or more days I have a 60watt mobile solar panel. The leisure battery is now 2 years old and I have always thought it seems to discharge abnormally quick as often, come the evening I will check the volts with a cheap usb/volt meter port which often states 12.6 although nothing has been plugged in. I do not have any set up for charging the battery when on EHU.
So based on what you say is this due to over charging/confusion of chemistry.
I have also never discharged the battery below 12.2v
Interested to hear your thoughts.
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Re: Twin batteries

Post by g8dhe » Mon Aug 26, 2019 3:57 pm

First we need to establish the "standard" voltages;

At rest a lead acid battery will generate 12.6-12.8 volts when fully charged.
If the voltage is higher than charging is occurring,
at 13.6 volts the normal losses from self discharge etc are balanced out and the battery is what is called as being Float charged, with neither loss or gain in charge.

Above 13.6 volts then there is charge going into the battery.

If the voltage exceeds 14.4 volts then the electrolyte is being broken down into Hydrogen and Oxygen - its best not to exceed this and alternators are set up to regulate for standard lead acid batteries at this voltage.
Whilst batteries have a stated capacity, this is NOT the usable capacity other than in the extreme, so a 100 AmpHour battery whilst it will supply a nominal 100 Amps for 1 hour or variations on this it will then be damaged and will not be able to be recharged to the same level. If you want a battery to last for the stated number of charge cycles then its quite important to not exceed more than 50% of the rated capacity i.e., 50 AmpHours.
A battery discharged to 50% level will give a voltage of around 10.8 to 11.00 volts.

Now as the newer types of chemistry get involved then the voltages don't vary a massive amount, however they can normally be recharged many more times, but the downside is that control of the voltage and what happens when the battery is fully charged needs much greater regulation for instance, Advanced Glass Mat (AGM) do not like being overcharged or kept at 14.4 volts when fully charged, if you don't drop the voltage back down to Float level (13.6 volts) then gassing occurs but the due to the much reduced volume of electrolyte in the battery its consequences are much more serious and the battery will permanently loose electrolyte and as they are sealed it can't be replaced ..... :-( Similar problems exist for all the variations VRLA/GEL batteries etc. all have there limitations which if exceeded will result in quicker failure, loss of capacity or recharge cycles.

The problems mentioned above can all be looked after by clever chargers that understand the battery type being used,
BUT and its a big BUT they all assume that all they are doing is charging the battery, not also supplying other loads in addition to charging, consequently in the simple set ups used in vans where the charger not only charges but supplies other loads at the same time, or when different systems charge a battery at different times the chargers don't know how much charge they have put into the battery so will either overcharge or undercharge as a consequence .... :-(

Most batteries, at a reasonable cost (circa £100 for 100 AmpHr) will have a 200± 100 cycle limit, and a 2 year warranty. I've had some batteries last a lot longer and more charge cycles (not always 50% cycles of course) and some that have lasted less.

In the example you quote I would suspect you will get quite an extended life beyond 2 years, but there are other factors that I have not mentioned like temperature both higher and lower than 20-30°C will also have a significant effect, but at this point the number of variables starts to get impossible to either quantify or record so its not worth digging further!
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Re: Twin batteries

Post by Roy748 » Mon Aug 26, 2019 5:52 pm

Thanks for a very detailed explanation. So may I clarify, connecting my leisure battery up to a 40watt solar panel following each drive out should not damage it, and the rate of discharge appears to be normal.
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Re: Twin batteries

Post by g8dhe » Mon Aug 26, 2019 6:04 pm

Yes 40 watt will be fine, needs a controller on it to be effective of course.
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Re: Twin batteries

Post by Roy748 » Mon Aug 26, 2019 6:09 pm

Yes controller fitted. Thanks for taking the time to explain in great detail.
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Re: Twin batteries

Post by Bob » Mon Aug 26, 2019 7:08 pm

As always, brilliant info.

Thanks Geoff. =D>
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