Solar charge?

Heppy

Heppy

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Recently changed my solar charger to a Victron smart charger with Bluetooth and all running good. Whilst rewiring I noticed a cable the same as the one from the solar panel to leisure battery running from leisure battery to starter battery. I disconnected at starter battery and checked with meter, it’s showing 12.6v. I didn’t think it was that simple to charge both batteries from solar or should it not be so.
Any advice much appreciated. Dave.
 
Not as simple as a cable running from the leisure battery to the starter as that would create one battery (as they are joined by this cable). However, installing a split charger (about £15 from a famous auction site) would solve this problem. This will basically look at the voltage from the first battery and only send a charge to the second battery once the first battery is fully charged.
 
DTDOG said:
Not as simple as a cable running from the leisure battery to the starter as that would create one battery (as they are joined by this cable). However, installing a split charger (about £15 from a famous auction site) would solve this problem. This will basically look at the voltage from the first battery and only send a charge to the second battery once the first battery is fully charged.
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This is a common myth about voltage sensing "split chargers".
They do NOT only activate when the first battery is fully charged. They activate when the on-threshold voltage is reached - which is long before any battery is fully charged.
 
Sorry, my mistake. You are right, but as this is generally set at around 13.7v then its as near as makes no difference to the statement I made.

The point I was making is, the first battery takes priority charge, then any spare is sent to the second battery.
 
So after numerous messages to wildebus i now have the right bit of kit on order.
Ablemail AMT-12 Battery Maintainer. Thanks again. Roll on the sunshine.
 
DTDOG said:
Sorry, my mistake. You are right, but as this is generally set at around 13.7v then its as near as makes no difference to the statement I made.

The point I was making is, the first battery takes priority charge, then any spare is sent to the second battery.
Click to expand...
Sorry, I have to disagree with the idea that the battery will be "as near as makes no difference" to be fully charged.

Yes, if a Battery was sitting at around 13.7V and was disconnected from any charging system, it really would be fully charged without a doubt.
But .... a Battery sitting at around 13.7V whilst attached to a charger is absolutely not close to full.

A little graph to illustrate this ....
1614876369608.png
Here the battery bank is below 70% State of Charge. If you take 50% as the base you never want to go below and 100% as full, under 70% would mean you have less than half the available capacity of the battery available and nowhere near full.
But check out the voltage of the battery - 14.18V. Well above the switch-on voltage threshold of a VSR.

I hate to labour the point but the battery would NOT be even close to fully charged at the point a VSR engages unless it actually started out close to fully charged when the engine was switched on.
Also, a VSR is just a relay, it is not an intelligent device, it is just a electrically activated switch and when it activates, the Starter and the Leisure Batteries are connected together and that is it - there is no concept of 'priority charge' and 'spare charge' with a relay.
The closest to intelligence when it comes to a relay-based charge system is probably the Victron Cyrix-ct, which monitors voltage levels over time and adjusts the on-threshold voltages based on how long the voltage has been above certain preset values - but even that is just a way to adapt when the relay switches on - when it is on, again it is just a switch that has been connected.

There is so much misinformation on how "split-chargers" operate on the internet, the erronous ones need to be responded to.
 
DTDOG said:
Sorry. Don't listen to me. I know nothing.
Click to expand...
Yeah your original advice to get a split charger was pretty good. Do not be disheartened the additional contributions made from our guru should be taken as further "enlightenment". We now all know more about split chargers and to cut to the chase that would probably be all the original poster requires, it may not fully charge the starter battery but may keep it at a level that will start the engine.
Without a split charger two batteries joined as stated in the original post is just plain wrong .....they could both go flat from domestic demand. Keep chipping in but be prepared for the shared wisdom. Live long and prosper.;)
 
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