Planet-9

Blowing headlights.

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2 captured repliesPartial discussion capture · Source accounts, not a confirmed diagnosis

THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

Discussion summary

YOUR RESEARCHBlowing headlights.

Leading reported evidence

Use on rvs

Performed · outcome unconfirmed

No successful repair reported for this finding.

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Reported fixes: 0
Unsuccessful attempts: 1
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Discussions that performed work without a confirmed outcome: 1

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Performed · outcome unconfirmed
There are many brands used on RVs to maintain house batteries.
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Blowing headlights.

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Leading evidence: 'Use on rvs' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Use on rvs' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.

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1 matching discussions · 2 captured posts examined · 1 partial discussions

Frequently discussed actions (1)

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Use on rvs

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed
There are many brands used on RVs to maintain house batteries.
Original post Read captured discussion
Blowing headlights.

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Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.

2 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.

Planet-9: 1 discussions

0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.

0 acknowledgements have no verified action link; they do not establish a repair result.

Generation: 20261026T133652Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1Original post

BMS stands for Battery Management System. A BMS is a circuit board built into lithium automotive cranking batteries. It does a few things like cuts off the battery when below freezing or when too hot. It regulates charge and cuts off when it gets drained to 25% charge. BMS also cuts off if the input voltage from the alternator if voltage happens to spike above 15.5 volts with a hard stop. Mine works as designed and averages about 14.7 V but on at least some cars like German go fast cars the voltage spikes to 16V plus for very short times. The battery stops accepting charge with a hard stop at 15.5V and that current with high voltage feeds the electrical system with a voltage spike. That blows headlights . These spikes are not a problem with AGM because they do not shut off and because lead acid batteries have about 1000 Farads of capacitance. I stopped using it for now because I have heard this problem also blows all sorts of electronics in vehicles besides just headlights . The techs at the two great suppliers of lithium, Dakota and Anti-Gravity both said to go back to AGM . They have heard of this Porsche problem. The 16 Volts is within the Porsche spec. The AGM is 45 pounds heavier than lithium and in my go fast application that will not fly. No pun intended. How can I filter out the voltage above 15.5 volts so I do not get a hard BMS stop with the current and voltage spike that is wreaking havoc? 2009 987.2

POST 2Original post

Possibly install a b-to-b charger (with a lithium profile) between the alternator and the Lithium battery to control the charge voltage going into the BMS. These chargers can step-down the voltage and amperage to a configurable level. There are many brands used on RVs to maintain house batteries.

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