Zenith Ch 650, UL 350iS Engine & Two Batteries

Always good to have two batteries in your airplane. This option shows how to use two SPST switches and one SPDT switch to link the alternator / voltage regulator-rectifier to charge Battery #1 or Battery #2.

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Comment by T.Y. on April 11, 2017 at 10:21pm

Hi Phil

UL engine is working out fine so far.  There is a nagging very minimal oil issue that appears to come from the prop hub area, am keeping an eye on it. That notwithstanding, the engine runs unbelievably smooth. There was a whole discussion about the UL 3560iS engine started by Mark recently.

As for me, since I signed up for the experimental world, I try to resolve issues myself. Had a bad Voltage Regulator/Rectifier that was instantly replaced by Robert Helms. Thought I had ECU issue, and Robert sent a new ECU instantly. Turned out issue was because of a chaffed spark plug wire, so on Robert's direction, sent ECU to Lawrence in Georgia.

Must say that, so far, the UL folks are fantastic, specifically Robert Helms in the Ozarks, and Patrick D. in Belgium. As well, I have had successful interactions with Lawrence in Georgia. They all have instantly responded to all of my concerns. Patrick in Belgium is simply fantastic.

When you get your wiring done for dual batteries, please share your ideas and diagram. Your approach seems unique and may be cool to try.


Comment by Phil Weston on April 9, 2017 at 10:49am
Good to know. My intentions at this point is to have a dual battery dual solinoid set up with the secondary battery isolated from the primary buss system and have that strictly for the ignition, ECU and back up fuel pump. If all the lights go out and the fire stops I would immediately switch to secondary battery for engine only components. I will keep that system isolated from the primary via a 40 amp circut breaker or relay, and rely on manual charging
Via the 30 amp relay. I'm sure plans will change as unforeseen things come up. How are you liking the UL engine? Thanks for the info, every little bit helps. Phil
Comment by T.Y. on April 9, 2017 at 9:01am

n my dual battery configuration, I have two capacitors, one for each battery. The UL engine factory recommends a capacitor in line with a battery. The best way this works is to plug the capacitors positive and negative wires directly to batteries positive and negative posts.

Here is a source for capacitors: the one you need is 63 volts and 68,000uf


Comment by T.Y. on April 9, 2017 at 8:47am

Just a quick clarification of paragraph 5 of my response to Philip.  I am not saying that I followed the Zenith factory's configuration. I meant to say that the Zenith Factory's CH 650 configuration uses only one continuous duty Cole Hersee solenoid for its two batteries rigged in parallel.

Comment by T.Y. on April 9, 2017 at 8:32am

Hi Philip:

I believe Zenith factory's CH 650 uses two batteries in a parallel configuration.  That gives that aircraft one large 12 volts with guts. This holds up longer when alternator fails.

Rigging batteries in series I believe gives you a different result in terms of voltage, say instead of 12volts, you get 24 volts, and so on.  Please correct this if I am off here. However, for experimental, we are trying to maintain 12 volts, but always looking for ways to improve and maximize power options.

You can rig two 12 volt batteries as primary 12 volts and backup 12 volts and use an isolator or a relay to switch between each one.  You see some of this rigging in some airplanes and marine applications, etc.

The UL engine factory has dual battery configuration. Notice that this is with a dual alternator, so the configuration has two voltage regulator/rectifiers, and then they use a relay to manage the two batteries.  Each battery has its own positive buss. In this configuration one battery serves as primary and the other as backup.

Following the Zenith Factory's CH 650 configuration, only one continuous duty solenoid is used. This parallel setup supplies a powerful 12 volts, and can support one or two positive buss. Each positive line ought to be fused, and 30 amp fuse is good enough for UL engine.

The Solenoids are the Cole Hersee insulated continuous duty SPST solenoid 12V - 24115. This is the same one supplied with the UL engine, You can buy this stuff from folks at the Zenith factory, or from partdeal.com/cole-hersee-insulated-continuous-duty-spst-solenoid-12v-24115.html

I do not think a diode is necessary (the factory's CH 650 does not have a diode attached to its solenoid), but in my configuration, I supported each solenoid with a diode (larger ring to aircraft ground and smaller ring to the small positive post on the solenoid) to keep positive hick-up from sneaking back up into sensitive instruments. This is just so that current is always dumped to ground after solenoid shut-off.

Hope this helps with your question. With batteries, fuel connection, etc, we always proceed carefully and tactfully so that nothing precious is ruined at the flip of a switch or up in the air.

Cheers and care.

Comment by Phil Weston on April 6, 2017 at 12:54pm
TY great video explanation. I'm curious as to which type of solenoids you use? Are they continuous duty? Would you foresee any problems with using a dual battery system in series with an isolator or do you think a parallel setup is better with separate dedicated buss.
Comment by Robert Helms on February 28, 2017 at 11:03am
Just to be clear... two batteries are not required.
Comment by Zenith.Aero on February 21, 2017 at 1:21pm

Good information. Thanks for sharing

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