Dodged a huge bullet on a dual battery solar setup.





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  1. #1
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    Default Dodged a huge bullet on a dual battery solar setup.

    This is the plywood base that I placed under my second battery in a Hz76 wagon under the hood.
    This battery is the same as the starter battery, a Willard (Sabat) low maintenance lead acid, and separated from the starter battery with a National Lunar solenoid system.


    All was OK, driving a fridge (50L weekender) in the back of the wagon, and some camp LED's and the odd mobile/tablet charge.
    Contrary to popular belief, these batteries are not sealed and a very slight sweat was always present on the breathers of both batteries. The alternator delivers up to 14.2 Volts but normally settles in at between 13.85 and 14 volts with both batteries linked and the fridge connected.

    I then went and added a Victron 75/15 BT controller with 2 by 120 watt panels on my roof top tent. I connect the solar panels when in camp or when traveling in game parks such as Central, or Kruger. The panels stay connected 24/7 while “Off road".

    The system seemed to work very well, and I was proud of the fact that the voltage on the second battery was always high enough to keep the National Lunar solenoid from connecting the two batteries. There was a bit more battery sweat on the second battery, but I expected this as I expected a bit of overcharging due to the higher temperatures under the hood and that fact that I do not have a temp controller as part of the Victron system (YET).

    So:
    Can this overcharging cause such a heat build-up in the battery? Enough to burn to plywood base almost to the point of ignition, or is the battery stuffed.
    Will the Victron temperature sensor cure this??

    I have attached the battery charging parameters on the controller and as they are settable, what should I adjust them to for this type of battery. To be honest, I don't remember being able to set the battery parameters on the earlier software, but I may be wrong. I remember having to choose the best battery fit from a list of Victron batteries.

    In any case, the point of this scribble is to enable me to fault find the reason for this excessive heat from the battery and to cure it, and to share the experience with others who may inadvertently be cooking their batteries, and to establish charging parameters going forward.
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  3. #2
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    That seems to be more than just a little excess heat...
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    In my opinion, the voltage settings are to high for a lead acid battery.

    The absorption voltage should not be more than the max voltage output of the alternator (14.1V)

    You will notice that the battery indicator shows 100% at battery voltage of 13.8V

    If reducing the parameters accordingly, you will avoid cooking the lead acid battery.
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    Quote Originally Posted by Kalahari Safari View Post
    .............
    My first thoughts as well
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    Just an absolute wild outside chance.

    Could it be the sweating onto the plywood that has caused that.
    Or did i misunderstand and you have felt the battery THAT hot.
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    Looks like plank was to close to exhaust manifold

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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    The plank was miles away from the exhaust, it definately was the battery, the part under the positive terminal part of the battery. Funny, no visible damage to the battery caseing by the way.

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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    I suspect this is indeed burnt, but in a 'charring' fashion.

    Burning of anything is really just oxidation -and it happens at differing rates.

    Newspaper 'browning' in the sun? -slow oxidation. Newspaper burning fiercely in a fire -fast oxidation.

    Oxidation is the basic process of life and organics - and is happening to everything all the time -just at differing rates.

    I think possibly the 'sweating' added fluid that caused considerable oxidation of the wood -charring, but not at speed to generate enough heat to actually set alight the volatiles released.

    I would look at fitting a metal base under the new battery.
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    Quote Originally Posted by Patrick L View Post
    I suspect this is indeed burnt, but in a 'charring' fashion.

    Burning of anything is really just oxidation -and it happens at differing rates.

    Newspaper 'browning' in the sun? -slow oxidation. Newspaper burning fiercely in a fire -fast oxidation.

    Oxidation is the basic process of life and organics - and is happening to everything all the time -just at differing rates.

    I think possibly the 'sweating' added fluid that caused considerable oxidation of the wood -charring, but not at speed to generate enough heat to actually set alight the volatiles released.

    I would look at fitting a metal base under the new battery.
    Agreed the sulphuric acid sweat would definitely cause that.
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    I just cant imagine that it was the battery that got that hot, surely all the battery water would have to boil off first otherwise it would not get more than 100degrees, and then the casing would be melted too
    Was there a cable near the timber?
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    No cabels run near this area and nothing is/has melted. The bracket is after market (FR) and painted with rattel can paint and this is relatively unscathed, so I am quite sure that the heat came from the battery. Acid sweat causing this should have buggered the paint on the bracket.

    I am happy to admit to overcharging I just want to confirm that the effects of this could be so devistating!!

    I would guess that most batteries under a hood of a car that does not have a smart alternator will over charge slightly when things warm up, but with the panels up and a good solar controller and no means of temp measurment on the battery, I guess that I pushed the batteries sence of humour.

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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    Which makes me think that the chargers with a temp sensor are actually a very good idea. My company sells them and they are on special at the moment. 8 stage intelligent charger. 5 year guarantee Swedish product. Going to fit a new AGM battery to my rig after lockdown and will definitely go this route. There is limited stock.
    FYI:
    Smart Easy20 (2A) - R842.00
    Smart Easy 50 (5A) - R1133.00
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    Look here: https://orizengroup.com/products/cha...y-charger.html
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    I've also cooked the battery in my Landy with the default settings of my Victron solar charger.

    After a lot of research and reading up on the matter I've found the default settings were way too high.

    So I've set the max boost voltage to 14.3V , float voltage to 13.8V (this might have to be lowered a bit) and the temperature compensation to -30.0mV/Deg C (that's -5mV per degrees per cell) for a normal Lead-Acid battery.

    It is VERY important that the solar charger is close to the battery to measure the temperature which the battery is at to do the correct temperature compensation. It is very dangerous to have the charger somewhere in the cool while you're charging the battery which is in the engine bay at some 50 or 60 degrees. Things are going to cook - I've learned the hard way.

    Victron sellers should have pointed this out.
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    This is a cheaper possible alternative from Micro Robotics for just R98.00. Rated for 10A and could be used on solar systems as well. 12V and 220V available.


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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    If that burn is a result of a battery getting too hot, surely the wood would have a neat square stamp/brand from the base of the hot battery, and the burn then radiating out from the contact point of the battery and the wood?
    That burn looks like it started at the edge of the wood and radiated in?
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    Quote Originally Posted by Graham View Post
    If that burn is a result of a battery getting too hot, surely the wood would have a neat square stamp/brand from the base of the hot battery, and the burn then radiating out from the contact point of the battery and the wood?
    That burn looks like it started at the edge of the wood and radiated in?
    Well, there is bugger all else which could have done that, trust me I would have noticed the little clues , like burnt out wireing loom, burnt paint on the battery holder, the exhaust having rerouted itself to the other side on the engine. It could be just one cell the only other clue is that it was under the Positive side of the battery.

    Funny thing is that the battery is still working, but the two ends are slightly puffed out, and I would imagine that it has lost a fair bit of electrolyte.

    I've also cooked the battery in my Landy with the default settings of my Victron solar charger.

    After a lot of research and reading up on the matter I've found the default settings were way too high.

    So I've set the max boost voltage to 14.3V , float voltage to 13.8V (this might have to be lowered a bit) and the temperature compensation to -30.0mV/Deg C (that's -5mV per degrees per cell) for a normal Lead-Acid battery.

    It is VERY important that the solar charger is close to the battery to measure the temperature which the battery is at to do the correct temperature compensation. It is very dangerous to have the charger somewhere in the cool while you're charging the battery which is in the engine bay at some 50 or 60 degrees. Things are going to cook - I've learned the hard way.

    Victron sellers should have pointed this out.

    I would think that if you had the battery temp sensor, the distance would not be too important as long as it can comunicate with the controller



    Anyone had any experiance with the Victron Blue toothe battery temp sensor??
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    Last edited by Gengis; 2020/04/21 at 02:32 PM.

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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    [QUOTE=Gengis;4374207]

    Funny thing is that the battery is still working, but the two ends are slightly puffed out, and I would imagine that it has lost a fair bit of electrolyte.

    Well from my understanding that is a definite sign that the battery has overheated / overcharged at some stage. Lets see what the others have to say.
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    Bulging points to overcharging
    That battery not going to handle a proper load
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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    slightly off topic whilst I was pondering this; since about 70's onwards vehicles are negative earth, and solar systems are conventionally positive earth (i was trying to see whether there was a fault mechanism for overcharging), I think when mixing solar to a vehicle that the solar reg and panels will be live w.r.t. vehicle so should fit fuse between battery + and standard solar charge regulator and be aware of "back-feeding" under fault conditions since the most positive panel + is connected to battery +.

    The regulation takes place in the negative lead, so IF the solar panel - contacts vehicle chassis it will bypass the regulator and overcharge.

    I'm pretty sure this is different or irrelevant using solar charger/controller and DC-DC units made for vehicles, but I suspect that Victron units made for household or boats would not expect negative earth?
    Last edited by KenBleekerKZN; 2020/04/22 at 11:28 AM. Reason: clarity

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    Default Re: Dodged a huge bullet on a dual battery solar setup.

    Ja, the negative side of solar chargers.
    So when the first models of solar controllers came out (pre MPPC) , they were controlled by FET transistors and these only came out in N type material (for the purpose of cost and manufacturing constraints). P was available at a price and not very high power. N type dictated that the negative side was controlled so it could not be tied to earth and it made the whole thing easier if the Positive side was.
    They now have P material available but because of existing designs and good old shithouse convention, and lazy designers, N type remained for all or most of the older type of controller.

    Enter the new age of MPPC, but they still want to separate the PV, the load and the battery and once again it easier to do so on the negative side of the components, so, although not strictly negative earth, some manufactures ask that you float the negative of at least one of the mentioned (PV Batt Load) preferably all 3. PV is easy to float, and in a home environment, the battery or load may also be.

    In a vehicle, the battery negative should be tied to the chassis so the PV and load negative should float. Easy for the PV and if you plan, for the load as well. But you must check that mounted systems like your fridge or charging station or lights do not have their negative sides tied to their casings / chassis/earth.

    It's a crap shoot as to which manufactures use which systems, so read the instructions carefully. My particular Victron demands that the PV and either the load or the battery float but it will not burn out if both load and battery are earthed, it just ties the load to the battery and defeats the purpose of a separate controllable load.

    I see that the latest National Lunar DC/DC and solar controller has one common negative for all 3 and this can be tied to the chassis as well. Good for them, no lazy designers at NL but please bend over if you want to purchase one.
    In summary, most solar controllers were NOT made for vehicles, and most have specific requirements or quirks regarding the negative/earthing connections so please read the instructions carefully if you are going to install them in a vehicle.

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