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jor asked

Victron BatteryProtect 12/24V 220A

Dear users,


I have a 26kW diesel generator with an external battery (charged by a battery charger). the generator is on automatic start/stop (with a victron multiplus / venus GX set-up). To avoid the battery (about 100Ah) from deep discharging (e.g. when the battery charger is malfunctioning), I have installed a BatteryProtect in between the battery and the generator. However with the BatteryProtect in between, the generator is not willing to start. The starter 'clenches' (?) but then 'dry clicks' when starting (i.e. not as if when the battery is low on voltage). I have tried multiple settings of the BatteryProtect but all give the same issue.

What setting of the BatteryProtect should I select? Or is there another problem that I'm overlooking? Below/attached some pictures. First picture is with the BP no in between battery & generator.



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 vbp3.jpg
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Thanks

GeneratorBattery Protect
vbp1.jpg (972.3 KiB)
vbp4.jpg (784.3 KiB)
vbp2.jpg (990.7 KiB)
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5 Answers
nickdb avatar image
nickdb answered ·

I would consult the manual. As far as I am aware the battery protect is one-way only. Sending power in reverse can damage the unit. This is documented in the very first section of the manual.


  1. Pay attention to the correct orientation. The BP is designed to allow current to flow from IN (battery) to OUT (load) terminals only. Reverse currents from OUT to IN terminals are strictly forbidden and will damage the device. If you wish to use the BP as a disconnection for a charge source, you must orient the unit in the system so that the current is flowing in the intended direction, IN to OUT.

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jor avatar image
jor answered ·

@nickdb , as far as I know, I am using the Battery Protect in accordance with its purpose/the manual, i.e. to avoid the generator/starter to draw energy from the battery when the battery would be low on voltage.

See schedule from the manual. I do not have the Relay, nor Remote, simply the Buzzer (and LED I think), hence cabling is less. But it is (and should be as far as I see) an interruption of the red cable (plus pole - sounds logic to me as the black one should be the neutral?). So current goes from the battery (red/+ pole) to the Battery Protect IN, then (inside the BP) from IN to OUT, then from OUT to the starter/generator.

I haven't set-up the cabling differently while (trying) to install. So the BatteryProtect should not be damaged inside.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·

I'm pretty sure that the generator also has an alternator to charge it's starter battery and that charging current would go through the BP in reverse.

I guess the starting current ist to high and the BP detects that as a short circuit.

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nickdb avatar image nickdb ♦♦ commented ·
My misunderstanding, incorrectly thought it was between the load and charger.
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jor avatar image
jor answered ·

@Matthias Lange - DE The generator does not have an alternator. That's the reason I need to charge the battery with an external battery charger, which thus risks not being charged properly.

Although I'm not an expert, even if there would be an alternator, I would expect that this alternator is connected directly to the plus pole for charging the battery, and is not ran from the alternator over the starter to the plus pole.

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Justin Cook avatar image
Justin Cook answered ·

I'm going to say most likely the massively high inrush current of the starter is triggering the short circuit protection of the BatteryProtect and causing it to shut down.

I'm entirely uncertain the purpose of the BatteryProtect there, but I would absolutely not advise putting it inline with a starter which can easily draw 4-5x its normal running current on lock-rotor startup. IE (and I've measured this) a 120A starter can draw 560A for ~30ms on lock-rotor startup, which will certainly upset a BatteryProtect.


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jor avatar image
jor answered ·

@Justin Cook if you say that a Battery Protect should not be used in this set-up, not sure then how to read the description that Victron gives (here) on the Battery Protect:

The BatteryProtect disconnects the battery from non-essential loads before it is completely discharged (which would damage the battery) or before it has insufficient power left to crank the engine.

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pwfarnell avatar image pwfarnell commented ·
If you have a starter battery which also supplies some other secondary loads, then the secondary loads are supplied through the BatteryProtect, then if the voltage is falling the BP isolates the secondary loads to keep the battery from discharging. The battery can tjen be used to start the engine when needed. It was never intended or suggested to be used to stop you starting an engine if the battery voltage was too low. DO NOT run a starter motor through a BP. You have entirely misunderstood what the BP is for.
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Justin Cook avatar image Justin Cook ♦♦ commented ·
Exactly as @pwfarnell has said, is the correct answer.
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Nev avatar image Nev commented ·

Agreed.

Our 300Ah LiFePO4 battery also starts the motorhome 3.9l turbo diesel engine often multiple times a day.

The 100A Victron BatteryProtect only protects and disconnects the house loads. Cut off is set at 12.0V. Never triggered in 10 years of daily use.

I have purposely lowered SOC to trigger the BP. Less than 10% SOC.

The battery still started the engine with ease.


Alternator output is separate unrelated wiring direct to the battery.

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