# BMS CL 12/100 is not stopping the charging of Smart Batteries **URL:** \ **Category:** DIY\ **Tags:** battery\_protect, marine, professional, victronconnect\ **Created:** [3 February 2025 21:35 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001 "2025-02-03T21:35:18Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![DominicNicholas](https://avatars.discourse-cdn.com/v4/letter/d/8dc957/32.png) [@DominicNicholas](https://community.victronenergy.com/u/DominicNicholas)\ **Post date:** [3 February 2025 21:35 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/1 "2025-02-03T21:35:18Z")
Hi Guys, Recently installed a BMS CL 12/100 and a battery protect 12/24 100A on a boat. The system has two Orion’s to charge the bow thruster and to charge the starter battery when the engine is not in use. It also has a MPPT 150/85. When the boat went into the water the batteries started being over charged and high temperatures experienced. The BMS when connected to Victron Connect says Alternator disconnected, Not allowed by battery, Battery above charge limit. The users have toggled off the BMS and the Battery Connect and the batteries are still receiving a charge. Could the BMS be faulty as it should not allow the altenator charge to pass through when the battery voltage and SOC has reached it’s max? ---
**Author:** ![pwfarnell](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/pwfarnell/32/2341_2.png) [@pwfarnell](https://community.victronenergy.com/u/pwfarnell)\ **Post date:** [3 February 2025 22:40 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/2 "2025-02-03T22:40:46Z")
You need to provide a diagram showing your set up. What lithium batteries do you have connected to the BMS. How are the Orions connected, how is the solar connected. Have you connected the ATC to anything. ---
**Author:** ![DominicNicholas](https://avatars.discourse-cdn.com/v4/letter/d/8dc957/32.png) [@DominicNicholas](https://community.victronenergy.com/u/DominicNicholas)\ **Post date:** [4 February 2025 16:11 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/3 "2025-02-04T16:11:21Z")
![image](https://europe1.discourse-cdn.com/victron/original/2X/3/379a1c4b0dacaa888be23c89d654e4fa21bde76f.png) This was the example followed for the connection. ![image](https://europe1.discourse-cdn.com/victron/original/2X/3/3505caf3e49093e18e13d0071e782c7a41150a48.png) This is the original wiring diagram. Removed the electronic charge separator, tied the house battery and alternator cables together. We inserted the engine battery Orion between these two connections, with the alternator and house cable as the input of the Orion and the engine battery cable as the output. The input for the BMS was tapped off of the Engine CB and the output from the Battery Protect connected back to the 300A fuse as seen in the drawing. Hope this helps. ---
**Author:** ![pwfarnell](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/pwfarnell/32/2341_2.png) [@pwfarnell](https://community.victronenergy.com/u/pwfarnell)\ **Post date:** [4 February 2025 20:42 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/4 "2025-02-04T20:42:13Z")
Again, I am trying to interpret your words and I may be wrong but you do not have a system as shown in the Victron drawing. > [@DominicNicholas](#): > > tied the house battery and alternator cables together If you attached the alternator cable to the house bank then the alternator will charge the house bank directly and the BMS will not control it, this is dangerous to the battery and to the alternator. The alternator can keep charging the house battery and overcharging it, getting it hot. You need to tie the alternator output to the engine battery. This connection from the alternator and engine battery then goes to the input of the BMS on the alternator port. ---
**Author:** ![DominicNicholas](https://avatars.discourse-cdn.com/v4/letter/d/8dc957/32.png) [@DominicNicholas](https://community.victronenergy.com/u/DominicNicholas)\ **Post date:** [5 February 2025 17:16 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/5 "2025-02-05T17:16:32Z")
Ok, i think we may be saying the same thing. I will do a sketch and post later. Thank you for your replies. ---
**Author:** ![DominicNicholas](https://avatars.discourse-cdn.com/v4/letter/d/8dc957/32.png) [@DominicNicholas](https://community.victronenergy.com/u/DominicNicholas)\ **Post date:** [6 February 2025 17:06 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/6 "2025-02-06T17:06:02Z")
Hi, sorry for the late response. I did a sketch of the connections. ![20250206_130225](https://europe1.discourse-cdn.com/victron/original/2X/f/fa865d17d1898375952f69fba3d723a610222459.jpeg) ---
**Author:** ![pwfarnell](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/pwfarnell/32/2341_2.png) [@pwfarnell](https://community.victronenergy.com/u/pwfarnell)\ **Post date:** [6 February 2025 18:14 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/7 "2025-02-06T18:14:01Z")
The connection shown in red should not be there, this is connecting the engine alternator output direct to the lithium batteries. The Battery Protect does not prevent current flowing backwards so the alternator can still charge the battery. Also, the solar charger will not be stopped from charging the batteries by the Battery Protect. ![IMG_20250206_181148](https://europe1.discourse-cdn.com/victron/original/2X/a/ae98a0f59c9c2b68c6ad192338a778457d75f49b.jpeg) ---
**Author:** ![pwfarnell](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/pwfarnell/32/2341_2.png) [@pwfarnell](https://community.victronenergy.com/u/pwfarnell)\ **Post date:** [6 February 2025 18:19 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/8 "2025-02-06T18:19:24Z")
Read the Battery Protect manual, you need one for the loads and one in the opposite direction for the solar controller. Ideally, the solar controller remote terminals should be controlled by the BMS ATC. ---
**Author:** ![DominicNicholas](https://avatars.discourse-cdn.com/v4/letter/d/8dc957/32.png) [@DominicNicholas](https://community.victronenergy.com/u/DominicNicholas)\ **Post date:** [6 February 2025 20:49 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/9 "2025-02-06T20:49:34Z")
“The Smart BatteryProtect is a uni-directional device. It can only deal with current in one direction, so either current to a load, or current from a charger, but not both currents at the same time. In addition to this, current only can only flow from the IN terminal to the OUT terminal. In case of use with a load, the battery connects to the IN terminal, and in case of use with a charger, the charger connects to the IN terminal.” This is from the manual, have I misinterpreted? ---
**Author:** ![pwfarnell](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/pwfarnell/32/2341_2.png) [@pwfarnell](https://community.victronenergy.com/u/pwfarnell)\ **Post date:** [6 February 2025 21:11 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/10 "2025-02-06T21:11:21Z")
You have a battery on one side of the battery protect and on the other you have a solar charger which will try to flow current into the battery. You also have the house loads which will try to take current out of the battery, so your Battery Protect is seeing currents in both directions which is not allowed. ---
**Author:** ![DominicNicholas](https://avatars.discourse-cdn.com/v4/letter/d/8dc957/32.png) [@DominicNicholas](https://community.victronenergy.com/u/DominicNicholas)\ **Post date:** [6 February 2025 22:20 UTC](https://community.victronenergy.com/t/bms-cl-12-100-is-not-stopping-the-charging-of-smart-batteries/21001/11 "2025-02-06T22:20:34Z")
Ok, I follow. My fix is a 2nd Battery Protect for the MPPT and connect the alternator and engine battery cable together so the alternator will only charge the engine battery and I can use the Orion 12/12 to charge the house battery.