Jocklandjohn Posted October 10, 2023 Share Posted October 10, 2023 I've got a starter/auxiliary set up which works just fine, but for prolonged running of diesel heater, as well as other equipment in very inclement conditions, the 80AH has been struggling, so I'd like to add a second aux battery for the winter months. I can't fit a larger AH battery in the battery box because it will only accept an 85AH max sized one beside the starter. I have space in an external side locker so I can use that for a third battery when required. Summer energy consumption is usually ok - the heater is rarely needed, and days (up here anyway) are very long so minimal lighting required, so its only the fridge thats being used (and the solar panel adds to the energy capacity too). However in the winter it can be a struggle - running the diesel heater, lights etc is necessary often from 4pm and the warm van means the fridge needs to run more too. Some work trips need several days on-site in remote areas, and often without actually driving anywhere - I go in, park up and work out of it for several days, so the alternator is not doing anything unless I run the van. If the weather is bad and I get all my gear soaked the heater will be running overtime as well. Anyway to the question - would this 'smart' Victron relay be suitable to add a third battery? I have an IBS battery monitor that manages the starter/auxiliary and their bumph shows a similar fancy relay that wil slot into the system and play nice with the others as a three battery setup. Only snag is it's over £200 which is a bit silly, whereas the Victron is about £35 which is more sensible. It *looks* to me like it will do the job, but could a sensible adult perhaps cast an eye on it please? This is the IBS relay which needs a mortgae (DBR - Dual Battery Relay). Which I would reaplce as wired with this below, the 120A version, Cyrix CT: Which has this wiring diagram in its guide: Am I missing anything here? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted October 10, 2023 Share Posted October 10, 2023 Are you intending on splitting up the supply, e.g. fridge to one battery, heater to another? Quote Link to comment Share on other sites More sharing options...
Jocklandjohn Posted October 10, 2023 Author Share Posted October 10, 2023 37 minutes ago, Bowie69 said: Are you intending on splitting up the supply, e.g. fridge to one battery, heater to another? Yes that was the plan. The fridge is currently managed directly off the solar controller (it has a dedicated load circuit) so it can be solar/battery depending on whats available and has all the low-voltage cut off stuff to protect the battery. So yes I was intending to wire the heater off aux battery 2. Quote Link to comment Share on other sites More sharing options...
simonr Posted October 10, 2023 Share Posted October 10, 2023 Personally, I would just connect the two Aux batteries through a voltage sensitive relay. https://www.12voltplanet.co.uk/durite-voltage-sensitive-split-charge-relay-12v-140a.html With the voltage sensing wire connected to the existing Aux battery. Then, when the existing battery is charging and Aux 1 is nearing full charge, it connects Aux 1 & 2 together. When charging stops, they are isolated. I would probably connect the heater to Aux 1 and the fridge to Aux 2 as Aux 1 is charged preferentially / first. The fridge not being cold is generally better than you being freezing! Quote Link to comment Share on other sites More sharing options...
Jocklandjohn Posted October 10, 2023 Author Share Posted October 10, 2023 (edited) 13 minutes ago, simonr said: Personally, I would just connect the two Aux batteries through a voltage sensitive relay. https://www.12voltplanet.co.uk/durite-voltage-sensitive-split-charge-relay-12v-140a.html With the voltage sensing wire connected to the existing Aux battery. Then, when the existing battery is charging and Aux 1 is nearing full charge, it connects Aux 1 & 2 together. When charging stops, they are isolated. I would probably connect the heater to Aux 1 and the fridge to Aux 2 as Aux 1 is charged preferentially / first. The fridge not being cold is generally better than you being freezing! Cheers Simon, very helpful. Curious though, whats the difference between that relay and the Victron one (just so I can understand this whole subject better!) Edited October 10, 2023 by Jocklandjohn Quote Link to comment Share on other sites More sharing options...
hurbie Posted October 10, 2023 Share Posted October 10, 2023 1 hour ago, Jocklandjohn said: Cheers Simon, very helpful. Curious though, whats the difference between that relay and the Victron one (just so I can understand this whole subject better!) as far as i can see : nothing .... to be fair , it doesn't charge your main battery first and then charges the second , it connects both battery's when the voltage is above 13.3 volts ..... so it charges both more or less at the same time .. Quote Link to comment Share on other sites More sharing options...
Jocklandjohn Posted October 10, 2023 Author Share Posted October 10, 2023 41 minutes ago, hurbie said: as far as i can see : nothing .... to be fair , it doesn't charge your main battery first and then charges the second , it connects both battery's when the voltage is above 13.3 volts ..... so it charges both more or less at the same time .. Thanks hurbie - thats what I *thought* from my reading of the bumph. Quote Link to comment Share on other sites More sharing options...
bushwhacker Posted April 6 Share Posted April 6 Hi to all, will a vsr mentioned above charge two different specification 12 volt batteries? I would like to run a second battery for my winch, diesel heater and some extra lights. Regards Mark. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted April 6 Share Posted April 6 4 hours ago, bushwhacker said: Hi to all, will a vsr mentioned above charge two different specification 12 volt batteries? I would like to run a second battery for my winch, diesel heater and some extra lights. A VSR is just a relay that switches on at a particular voltage, usually the alternator charges the main battery and then the VSR kicks in and connects the 2nd battery so the alternator is then charging both. Specification won't matter too much as long as they're both standard lead acid batteries designed to be charged by a regular alternator. Quote Link to comment Share on other sites More sharing options...
bushwhacker Posted April 6 Share Posted April 6 Excellent, thanks. VSR should suit my requirements then. 👍 Quote Link to comment Share on other sites More sharing options...
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